1. Field of the Invention
This invention relates to a rearview mirror and, more particularly, to an electrically driving system for foldable rearview mirrors of motor vehicles.
2. Description of the Prior Art
Outer rearview mirrors are suitably folded at their mirror body to reduce their length when parking or storing motor vehicles. Recently, there are electrically foldable rearview mirrors whose mirror body is turned form an erected position to a folded position with a reversible motor mounted in the mirror body. There is proposed a driving system in which relays and selfholding circuits are provided to let the motors be rotated and stopped indirectly in response to the operation of a switch in stead of rotating and stopping the motors directly by operating a switch.
Such an improved driving system is disclosed for example in Japanese Patent Application Laid-Open No. Sho. 61-113533. In this system, a motor circuit for each of the right and left mirror bodies includes an erecting relay and its holding circuit which are operated when turning the mirror body from the folded position to the erected position, as well as folding relay and its holding circuit which are operated when turning the mirror body from the erected position to the folded position. At either of the turning ends of the mirror body, a limit switch is operated to release a self-holding state so as to step the motor automatically. In this driving system, however, the limit switches for detecting the erected and the folded positions of the left and right mirror bodies can only put opening relays in a non-exited condition, and they can not put both relays and motors out of operation. Besides, it is necessary to provide reacting and folding relays and self-holding circuits for each of the left and right reversible motors. Therefore, the overall circuit is complicated, is inevitably large in size, requires a large number of assembling steps and dictates high cost of manufacture.
In Japanese Patent Laid-Open No. Sho. 61-105247 this applicant has disclosed a driving circuit for electrically foldable rearview mirrors which comprises a single-pole momentary push button switch, erecting and folding relays operated with the said bush button switch, a plurality of reversible motors rotated by the operation of either of the said push button switch and a folded-state judgment circuit provided with a PNP-type transistor. This driving circuit has a operation mode in which the folding relay is preferentially operated by the operation of the momentary push button switch, it is judgmented under the "ON" condition of the folding circuit whether both of the left and right mirrors are in the folded positions, both of the left and right mirrors are erected only when they are in the folded positions, either or both of the left and right mirrors are folded when they re not in the folded positions. That is, when both of the left and right mirror bodies are in the folded positions, the folding relay is excited first by pushing the push button, then plus voltage is impressed to an emitter of the transistor through a transfer contact. Because of earth potential applied to a base of the transistor through the closed single-pole single-throw switch interlocked with the push button, the transistor is put into "ON" condition at the same time, and the erecting relay is excited. Since the transfer contact of the folding relay changes over by the excitation of the erecting relay to demagnetize the folding relay, and since the erecting relay is self-held with the limit switch and so, the motors of the left and right mirror bodies are rotated to an erecting side. When the mirror bodies reach the erecting ends, the limit switch is mechanically forced open, and the motors are stopped by closing the motor circuits.
When one of the left and right mirror bodies is in the folded position, and the other is in the erected position or in the intermediate position between the erected and folded states, the unfolded mirror body is laid back and both of the mirror bodies are stopped in the folded position by the first operation of the push button, then the mirror bodies on both sides are turned in the erecting direction. That is, when the other mirror body is in the unfolded position, as described above, the folding relay is exited. Then the transfer contact of the folding relay changes over to impress plus voltage to the base of the PNP-type transistor through the single-pole single-throw switch interlocked with the limit switch and the push button switch o the unfolded position side. Since the transistor is not put to "ON" by this impressed voltage, the erecting relay is not excited, but because of the self-held folding relay the motor of mirror body is turned from the unfolded position to the folded position. At one turning end of the mirror body the limit switch on the folding side is opened to stop the motor. Since a single-pole single-throw switch interlocked with the push button is provided on the base input side of the PNP-type transistor, no folding operation begins immediately as long as the next operation of the push button is not performed after the mirror body has been folded. The push button switch and the single-pole single-throw switch interlocked therewith, however, form a two-pole single-throw operational switch. Therefore, the over fall circuit is complicated in construction, is low in degree of freedom of design and is large in size. It requires also a large number of wires between the switches and the control circuit as well as multi-pole connectors, and dictates high cost of manufacture.
An object of the present invention is to provide a compact and cheap driving circuit operated with only one momentary single-pole single-throw switch.
Another object of the present invention is to provide an electrically driving circuit for foldable rearview mirrors which ensures an accurate folding operation and can be provided at low cost.